An update to my problem:
I have tried to load OS 2.0 for VA 76 and everything went apparently fine: I loaded the two disks set and then re-powered the keyboard. At this point I was asked to perform some fine-tuning of the pitch bend (which I did) and of the touchscreen; the instructions on the screen itself asked me to press a point at the lower left corner, I did that and nothing happened; I tried the same operation three times and then gave up when I realized that the VA 76 has a larger touchscreen and so the settings were of course different from my VA 7.
At this point I loaded OS 1.03 and everything went fine: the keyboard is working again and I am able to play as before, except that I have lost all the new features of OS 2.0 (what I am especially missing is the Performance database).
I hope that my experience can be useful to other VA 7 owners: always make of copy of your OS on a couple of floppy disk!
Regards,
Andrea
(still waiting, like Roel some time ago...)